How do we know Gaius was a fellow helper to the truth?

Gaius exemplifies what it means to be a fellow helper to the truth by providing hospitality and support to traveling gospel preachers, reflecting his commitment to advancing the gospel without taking from the Gentiles. His actions highlight the importance of using one's resources for the kingdom of God, as noted in 3 John where John commends him for facilitating gospel work. Being a fellow helper is a privilege and a vital role in the church, showing gratitude for God’s grace by contributing to the furtherance of the gospel.